The largest fish in the world is very mysterious and endangered

Don’t let the name fool you. Whale sharks are not whales. They are sharks.

And they are the largest species of fish on the planet. They can grow as long as a city bus. In addition, scientists recently closed that whale sharks — which have unique spots on their bodies that resemble fingerprints — are Earth’s largest living omnivores, officially dethroning Alaska’s Kodiak bears. (Whale sharks eat shrimp, plants, and more.)

Sadly listed as Vulnerable by the International Union for Conservation of Nature, this large species is mysterious and never ceases to amaze biologists.

“What I love most about whale sharks is that they challenge everything we think we know about sharks.”

“What I love most about whale sharks is that they challenge everything we think we know about sharks,” Alistair Dove, marine biologist and vice president of the Atlanta-based Georgia Aquarium, told Mashable.

Mysterious Creatures

One of the most confusing things about whale sharks is how they give birth. There is a hypothesis that female whale sharks make their eggs, the eggs hatch inside them, and they eventually release live babies into the water. But so far, researchers have yet to see a whale shark mating or giving birth. However, fishermen have harpooned, killed and then cut opened a pregnant female shark at a fish market in Taiwan in 1995. Inside were about 300 dead baby whale sharks, which is an unusually high number for a shark.

When When the fishermen dissected the animal, they realized they had never seen a whale shark with hundreds of pups and called local marine scientists, said Jennifer Schmidt, molecular biologist and director of the Shark Research Institute in New Jersey. The pups were then safely collected and frozen.

“We can never track an animal for its entire life.”

Years later, Schmidt and her team decided to do it carry out a genetic analysis on 10 percent of the puppies to determine their paternity. They found that all of the pups had the same father, suggesting that whale sharks could mate once, store the sperm, and eventually fertilize their own eggs.

It is difficult to know what life is like for whale sharks. That’s because they’re long-lived animals, likely surviving well over a century. This makes it difficult to track an individual animal and its migration throughout its lifetime.

“We can never track an animal for its entire life,” Schmidt said.

(Typically, fish have the number of rings on their bones indicating how old they are. But whale sharks don’t have hard bones like other fish, and calculating their age becomes difficult, Georgia Aquarium’s Dove told Mashable.)

Endangered Creatures

Knowing how whale sharks behave and how they migrate is critical to the conservation of this endangered species. We’ve lost an estimated 50 percent of whale sharks in the last 75 years, said Gonzalo Araujo, a whale shark researcher and also a member of the International Union of Conservation of Nature’s Shark Specialist Group.

The biggest threat to whale sharks is fishing — including accidental catch or bycatch — despite attempts to protect them in most countries, Dove told Mashable. “People in small villages in developing countries are fortunate to catch a whale shark. That’s enough to feed their village for some time,” he explained.

The next big threat, Dove said, is ships colliding with whale sharks. Whale sharks, which spend a lot of time on the sea surface feeding on plankton, are easily hit by commercial fishing vessels. Unlike whales, which tend to swim after they die, whale sharks often sink after they are killed. “Merchant shipping can be a silent killer,” he said.

“Merchant shipping can be a silent killer.”

Climate change could also threaten the dwindling whale shark population. One of their main food sources, plankton, is sensitive to changing conditions in the oceans like temperature and acidity, and whale sharks will redistribute as their prey change, Araujo told Mashable. They might not succeed in new oceanic regions. “But that will extend over longer periods of time,” he said.

Another potential threat to their survival is looming, and that is plastic pollution. Whale sharks are filter feeders, which means they make a living by ingesting vast amounts of water and filtering out small animals. They can’t differentiate between plankton and small pieces of plastic, Dove said. We don’t yet know the impact of ingesting this plastic on their health, he noted.

Despite years of whale shark research, we still know relatively little about their biology and behavior. To better protect these animals, we need to know where they are born, where they breed and where their babies go, Dove pointed out. Since the Tyrannosaurus rex Whale sharks, stomping around millions of years ago in the Cretaceous Period, were doing their thing in the ocean. “I think we have a responsibility to figure out how to live with them a little bit better,” Dove said.